In the end the Party would announce that two and two made five, and you would have to believe it. It was inevitable that they should make that claim sooner or later: the logic of their position demanded it … And what was terrifying was not that they would kill you for thinking otherwise, but that they might be right. For, after all, how do we know that two and two make four? Or that the force of gravity works? Or that the past is unchangeable? If both the past and the external world exist only in the mind, and if the mind itself is controllable…what then?
— from George Orwell’s “Nineteen Eighty-Four”
Photo credit: Gage Skidmore from Peoria, AZ, United States of America [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)%5D